1. Field of the Invention
This invention relates to infrared heaters in which a refractory body is heated by means of a gas-fired burner to an elevated temperature causing it to emit infrared radiation, and more particularly, to such infrared heaters adapted to provide heat energy to cooking vessels, such as bowl-shaped cooking woks.
2. Description of Related Art
Wok cooking involves the application of intense heat to a wok, a metal cooking vessel having a convex bottom. Typically, the heat is provided by a gas-fired burner. In a wok range, a wok cooking station typically consists of a cylindrical or tubular wok support that rises from a heat source such as a gas-fired burner through the top surface of the range. Conventional wok burners are generally only about 15-20% efficient.
Heat conduction through the range top is an inevitable consequence of the operation of a wok heater or burner. Wok cooking typically involves temperatures up to about 2100° F. in order to seal the flavor of the food being cooked and to bind the spices and accents to the food. During cooking, the heat generated by the burner is chimneyed upward through the wok support to the wok; however, a significant amount of heat is also conducted through the wok support to the range top resulting in potentially damaging and dangerous high range top temperatures. Conventionally, cooling means, such as the use of a cooling fluid, e.g. water, are used to reduce the range top temperatures. For continuously operating wok ranges, the amount of water employed may be substantial. One solution for eliminating the need for such cooling fluids is taught by U.S. Pat. No. 6,718,967 B2 to Luther. There, a refractory insulating material is incorporated into the support structure wherein the wok support includes a tubular support structure having internal space in its wall in which the refractory insulating material is disposed.
There are essentially three ways in which heat is transferred from a higher temperature source to a lower temperature receiver: conduction, convection, and radiation. Of these, radiant heating provides substantially instantaneous heating compared to the relatively slow heating afforded by convective heating and is potentially more efficient than either convective or conductive heat transfer. U.S. Pat. No. 4,889,103 to Fraioli teaches an infrared wok heater comprising a ribbon-type burner head fed with a pressurized mixture of air and gas that is expelled from the head through a cylindrical array of minute jet openings to produce an omnidirectional flame when ignited and comprising a block of refractory material which, when heated to an elevated temperature, emits infrared radiation. The block has superposed base, intermediate, and top sections, the base section having a cavity therein whose central zone communicates with central openings in the intermediate and top sections, and an outer zone which communicates with a circular array of bores in the intermediate and top sections. The burner head is disposed within the block of refractory material so that the flame projected from the lower portion of the cylindrical array impinges on the wall of the cavity in the base section, as a result of which infrared radiation is emitted through the bores to provide secondary beams, while the flame projected from the upper portion of the array impinges upon the wall of the opening in the intermediate section, as a result of which infrared radiation is emitted through the opening to provide a main beam. The wok is seated above the block so that the central portion of the wok is heated by the main beam and the peripheral region of the wok is heated by the outer beams.